Transmissive and reflective type liquid crystal display

ABSTRACT

Disclosed is a transmissive and reflective type LCD. In the LCD, a second substrate faces a first substrate. A liquid crystal layer is formed between the first substrate and the second substrate. A first polarizing plate is formed on an outer surface of the first substrate. A second polarizing plate is formed on an outer surface of the second substrate. A backlight is arranged for irradiating incident light onto the polarizing plate. A transparent transflective film is arranged between the first polarizing plate and the backlight for partially reflecting and partially transmitting the incident light. The transparent transflective film includes at least a first layer and a second layer, the first and second layers having different refractivity indexes from each other and are alternatively stacked. By a restoring process occurring between the transflective film and the backlight, a predetermined amount of the incident light is transmitted through the transflective film repeatedly, so that transmissivity and light efficiency are enhanced.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Divisional of U.S. patent application Ser. No.10/183,143, filed on Jun. 26, 2002, the contents of which are fullyincorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a liquid crystal display, and moreparticularly, to a transmissive and reflective type liquid crystaldisplay in which the display operation is carried out in reflection modeand transmission mode.

2. Description of the Related Art

Liquid crystal displays (LCDs) have become displays of choice among thevarious developed flat panel type displays because they are much slimmerand lighter than other types of displays. They also require lowerdriving voltage and lower power consumption.

LCD displays are classified as transmission type which display imagesusing an external light source such as a backlight, as reflection typewhich display an image using natural light, and transmissive andreflective type which display in a transmission mode using an internallight source provided in the display itself at indoors or a dark placewhere an external light source does not exist and the display operatesin a reflection mode to display images by reflecting external incidentlight in a high brightness environment such as at outdoors.

LCDs can also be classified depending on the way they are driven. Forexample, In the passive matrix type, pixels in the LCDs are driven usinga root-mean-square (rms) of a difference between voltages applied tosignal lines and scanning lines, while a line addressing in which asignal voltage is applied to all of the pixels at the same time iscarried out. In the active matrix type, pixels are driven by a switchingelement such as a MIM (Metal-insulator-metal) device or a thin filmtransistor.

FIG. 1 is a sectional view of a conventional transmissive and reflectivetype LCD, and shows an active matrix type LCD using the thin filmtransistor.

Referring to FIG. 1, the conventional transmissive and reflective typeLCD includes a first substrate 10, a second substrate 40 arranged facingthe first substrate 10, a liquid crystal layer 50 formed between thefirst substrate 10 and the second substrate 40, and a light source,i.e., a backlight assembly 60 disposed at a rear side of the firstsubstrate 10.

The first substrate 10 includes a first insulating substrate 11, a thinfilm transistor 25 formed on the first insulating substrate 11, apassivation film 30 having a contact hole 32 for exposing a part of thethin film transistor 25, a transparent electrode 34, and a reflectionelectrode 36. The thin film transistor 25 includes a gate electrode 12,a gate insulating film 14, an active pattern 16, an ohmic contactpattern 18, a source electrode 20, and a drain electrode 22. Thetransparent electrode 34 functions as a pixel electrode for transmittinglight that is generated from the backlight 60 and is then incidentthrough the first substrate 10. The transparent electrode 34 isconnected to the thin film transistor 25 formed on every unit pixelregion on the first substrate 10. The reflection electrode 36 reflectsexternal light that is incident through the second substrate 40 and atthe same time functions as another pixel electrode. The transparentelectrodes 34 include regions of a transmission part T and a reflectionpart R for reflecting the external light incident through the secondsubstrate 40.

The second substrate 40 includes a second insulating substrate 42, acolor filter 44 comprised of RGB pixels for displaying colors whilelight is transmitted therethrough, a black matrix 46 for preventing thelight from being leaked between the pixels, and a transparent commonelectrode 48.

The liquid crystal layer 50 is made of 90° twisted nematic (TN) liquidcrystal, and has an approximately 0.24 of Δnd which is a product ofanisotropy Δn in refractive index and thickness d of the liquid crystallayer 50.

Also, according to an alignment direction of the liquid crystalmolecules, a first polarizing plate 54 and a second polarizing plate 58are respectively attached to external surfaces of the first and secondsubstrates 10 and 40 so as to transmit only polarized light in aspecific direction. The first and second polarizing plates 54 and 58 areall linear polarizers in which each polarizing axis of the first andsecond polarizing plates 54 and 58 is orthogonal to each other.

Between the first substrate 10 and the first polarizing plate 54, andbetween the second substrate 40 and the second polarizing plate 58,there are respectively arranged a first ¼ wavelength phase differenceplate 52 and a second ¼ wavelength phase difference plate 56. Each ofthe ¼ wavelength phase difference plates 52 and 56 functions to convertlinearly polarized light to circularly polarized light, or vice versa bycausing a phase difference of ¼ wavelength between two polarizationcomponents that are orthogonal to each other and are parallel to theoptical axes of the ¼ wavelength phase difference plates 52 and 56.

Hereinafter, there are respectively described operations in thereflection mode and the transmission mode in the conventionaltransmissive and reflective type LCD shown in FIG. 1.

FIGS. 2A and 2B are schematic views for illustrating an operation of theconventional LCD in the reflection mode.

First, when a pixel voltage is not applied (OFF), as shown in FIG. 2A,light that is incident from an outside is transmitted through the secondpolarizing plate 58, so that the light is linearly polarized in adirection parallel to the polarizing axis of the second polarizing plate58. The linearly polarized light is transmitted through the second ¼wavelength phase difference plate 56, so that the linearly polarizedlight is converted onto left-handed circularly polarized light. Theleft-handed circularly polarized light is transmitted through the liquidcrystal layer 50, so that the left-handed circularly polarized light islinearly polarized in a direction vertical to the polarizing axis of thesecond polarizing plate 58, and is then incident onto the reflectionelectrode 36. The linearly polarized light, which is reflected by thereflection electrode 36, is transmitted through the liquid crystal layer50, so that the linearly polarized light is converted onto theleft-handed circularly polarized light. The left-handed circularlypolarized light is transmitted through the second ¼ wavelength phasedifference plate 56, so that the left-handed circularly polarized lightis linearly polarized in a direction parallel to the polarizing axis ofthe second polarizing plate 58. And then, the linearly polarized lightis transmitted through the second polarizing plate 58, so that a whiteimage is displayed.

When a maximum pixel voltage is applied (ON), as shown in FIG. 2B, lightthat is incident externally is transmitted through the second polarizingplate 58, so that it is linearly polarized in a direction parallel tothe polarizing axis of the second polarizing plate 58. The linearlypolarized light is transmitted through the second ¼ wavelength phasedifference plate 56, so that it is converted onto left-handed circularlypolarized light. The left-handed circularly polarized light istransmitted through the liquid crystal layer 50 without variation in thepolarization state, and is then incident onto the reflection electrode36. The light, which is incident onto the reflection electrode 36, isreflected by the reflection electrode 36, so that it is converted toright-handed circularly polarized light and the converted right-handedcircularly polarized light is transmitted through the liquid crystallayer 50. Thus, the right-handed circularly polarized light, which hasbeen passed through the liquid crystal layer 50, is transmitted throughthe second ¼ wavelength phase difference plate 56, so that it islinearly polarized in a direction perpendicular to the polarizing axisof the second polarizing plate 58. The linearly polarized light isshielded by the second polarizing plate 58, so that a black image isdisplayed.

FIGS. 3A and 3B are schematic views for illustrating an operationmechanism of the transmission mode.

When a pixel voltage is not applied (OFF), as shown in FIG. 3A, lightthat is irradiated from a backlight disposed below the first polarizingplate 54 is incident onto the first polarizing plate 54, and only lightpropagating in a direction parallel to the polarizing axis of the firstpolarizing plate 54 is transmitted through the first polarizing plate54. At this time, since the polarizing axis of the first polarizingplate 54 is perpendicular to that of the second polarizing plate 58, thelight that has been passed through the first polarizing plate 54 isconverted onto light linearly polarized in a direction perpendicular tothe polarizing axis of the second polarizing plate 58. The linearlypolarized light is converted onto a right-handed circularly polarizedlight by a first ¼-wavelength phase difference plate 52. Theright-handed circularly polarized light is transmitted through atransparent electrode 34, and is then incident to a liquid crystal layer50. The right-handed circularly polarized light is transmitted throughthe liquid crystal layer 50, so that it is linearly polarized in adirection parallel to the polarizing axis of the second polarizing plate58. The linearly polarized light is transmitted through a second¼-wavelength phase difference plate 56, so that it is converted onto theright-handed circularly polarized light. At this time, since only alight component propagating in a direction parallel to the polarizingaxis of the second polarizing plate 58 can be transmitted through thesecond polarizing plate 58, only about 50% of the right-handedcircularly polarized light is transmitted through the second polarizingplate 58. Accordingly, there is a light loss of about 50%, and an imagehaving a moderate brightness is displayed.

Meanwhile, although not shown in the drawings, an optical path of theincident light becomes different at a region where a metal layer, suchas the gate line, the data line, or the reflection electrode exists inthe transmission mode. In other words, light that is incident from thebacklight is transmitted through the first polarizing plate 54, so thatit is linearly polarized in a direction parallel to the polarizing axisof the first polarizing plate 54. The linearly polarized light istransmitted through the first ¼ wavelength phase difference plate 52, sothat it is right-handed circularly polarized. The right-handedcircularly polarized light is reflected by metal layers, and becomeleft-handed circularly polarized. Then, the left-handed circularlypolarized light is transmitted through the first ¼ wavelength phasedifference plate 52, so that it is linearly polarized in a directionparallel to the polarizing axis of the first polarizing plate 54.Accordingly, the linearly polarized light is absorbed in the firstpolarizing plate 54, and does not return to the backlight. Thus, thelight reflected by the metal layers is not reproduced and disappears, sothat an overall light efficiency is lowered.

When a maximum pixel voltage is applied (ON), as shown in FIG. 3B, lightthat is irradiated from a backlight disposed below the first polarizingplate 54 is incident onto the first polarizing plate 54, so that onlylight propagating in a direction parallel to the polarizing axis of thefirst polarizing plate 54 is transmitted through the first polarizingplate 54. The light linearly polarized by the first polarizing plate 54is converted into a right-handed circularly polarized light after beingtransmitted through the first ¼ wavelength phase difference plate 52.The right-handed circularly polarized light is transmitted through thetransparent electrode 34, and is then incident onto the liquid crystallayer 50. The right-handed circularly polarized light is transmittedthrough the liquid crystal layer 50 without variation in thepolarization state, and is linearly polarized in a direction orthogonalto the polarizing axis of the second polarizing plate 58 after beingtransmitted through the second ¼ wavelength phase difference plate 56.Afterwards, the light linearly polarized in the direction orthogonal tothe polarizing axis of the second polarizing plate 58 is not transmittedto the second polarizing plate 58, so that a dark image is displayed.

As described above, since the conventional transmissive and reflectivetype LCD has to be provided with the wide band ¼ wavelength phasedifference plates 52 and 56 covering an overall frequency band of thevisible ray, as well as the first and second polarizing plates 54 and 58with respect to each of the first and second substrates 10 and 40,manufacturing cost is increased as compared with the transmission typeLCD. Also, since the polarization characteristic in the transmissionmode causes light loss of about 50%, there are drawbacks in that a lighttransmissivity decreases by about 50% and contrast ratio (C/R) islowered.

Further, since Δnd of the liquid crystal layer 50 is only about 0.24 μmwhich is a half of Δnd (about 0.48 μm) of the conventional transmissiontype LCD, the cell gap of the liquid crystal cell should be decreased toa level of about 3 μm, and the refractive anisotropy Δn of the liquidcrystal also should be decreased. Accordingly, there is a need for atransmissive and reflective type LCD device and method which avoidsaforementioned problems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is to solve the aforementionedproblems of the conventional art, and it is an object of the presentinvention to provide a transmissive and reflective type LCD capable ofsimplifying a structure of a liquid crystal cell and decreasing lightloss in the transmission mode.

In one aspect, there is provided a transmissive and reflective type LCDcomprising a first substrate, a second substrate, a liquid crystallayer, a first polarizing plate, a second polarizing plate, a backlight,and a transparent transflective film. In the transmissive and reflectivetype LCD, the second substrate has an inner surface that is arrangedfacing the first substrate, and the liquid crystal layer is formedbetween the first substrate and the second substrate. The firstpolarizing plate is formed on an outer surface of the first substrate.The second polarizing plate is formed on an outer surface of the secondsubstrate, the outer surface being opposite to the inner surface of thesecond substrate. The backlight is arranged for irradiating incidentlight onto the first polarizing plate. The transparent transflectivefilm is arranged between the first polarizing plate and the backlightfor partially reflecting and partially transmitting the incident light.The transparent transflective film includes at least a first layer and asecond layer having different refractivity indexes from each other andare alternatively stacked.

According to another aspect of the invention, there is provided atransmissive and reflective type LCD for partially reflecting andtransmitting incident light, comprising an LC cell, a first polarizingplate, a second polarizing plate, a backlight and a transparenttransflective film. The LC cell includes a first substrate, a secondsubstrate having an inner surface that is arranged to face the firstsubstrate, and a liquid crystal layer formed between the first substrateand the second substrate. The first polarizing plate is formed on anouter surface of the first substrate. The second polarizing plate isformed on an outer surface of the second substrate that oppositely facesthe inner surface of the second substrate. The backlight is arranged ata rear side of the first polarizing plate. The transparent transflectivefilm is arranged between the first polarizing plate and the backlight,and has a plurality of layers in which a first layer and a second layerhaving different refractivity indexes from each other. The transmissiveand reflective type LCD has a reflection light path along which theincident light is incident onto the LC cell from a front side of the LCcell, is reflected by the transflective film, and is output through thefront side of the LC cell. And, The transmissive and reflective type LCDhas a transmission light path along which the incident light is incidentonto the LC cell from a rear side of the LC cell, is transmitted throughthe transflective film, and is output through the front side of the LCcell.

The transmissive and reflective type LCD of the invention does notrequire a reflection electrode within LC cell or a ¼-wavelength phasedifference plate on each of the upper substrate (second substrate) andthe lower substrate (first substrate). Hence, compared with theconventional transmissive and reflective type LCD, the transmissive andreflective type LCD of the present invention is simpler and more easilymade.

Further, it is possible that the transflective film of partially beingtransmitted and reflecting incident light performs both functions of thereflection electrode and the transparent electrode at the same time, anda recycling process of light is lastingly generated, so that light lossis not generated in the transmission mode. Accordingly, compared withthe conventional transmissive and reflective type LCD, the transmissiveand reflective type LCD of the invention has an enhanced transmissivity.Also, since the transmissive and reflective type LCD of the inventiondoes not utilize the ¼ wavelength phase difference plate, the light thatis incident from the backlight and is then reflected by metal regions ofLC cell is recycled and again used, so that it becomes possible toenhance an overall light efficiency.

Furthermore, since the optical conditions applied to the liquid crystalof the conventional transmissive and reflective type LCD can beidentically applied to that of the transmissive and reflective type LCDof the present invention, there is no degradation in reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and other advantages of the present invention willbecome more apparent by describing in detail exemplary embodimentsthereof with reference to the attached drawings in which:

FIG. 1 is a sectional view of a conventional transmissive and reflectivetype LCD;

FIGS. 2A and 2B are schematic views for illustrating a conventionaltransmissive and reflective type LCD of FIG. 1 in a reflection mode;

FIGS. 3A and 3B are schematic views for illustrating a transmissive andreflective type LCD of FIG. 1 in a transmission mode;

FIG. 4 is a sectional view of a transmissive and reflective type LCD inaccordance with an embodiment of the present invention;

FIG. 5 is a schematic view showing a structure of the transflective filmshown in FIG. 4;

FIGS. 6A and 6B are sectional views for illustrating a light scatteringlayer that is applicable to the transmissive and reflective type LCD ofFIG. 4;

FIGS. 7A and 7B are schematic views for illustrating the transmissiveand reflective type LCD of FIG. 4 applied in a reflection mode;

FIGS. 8A and 8B are schematic views for illustrating the transmissiveand reflective type LCD of FIG. 4 applied in a transmission mode;

FIGS. 9A and 9B are schematic views for illustrating the transmissiveand reflective type LCD of FIG. 4 applied in a reflection mode;

FIGS. 10A and 10B are schematic views for illustrating the transmissiveand reflective type LCD of FIG. 4 applied in a transmission mode; and

FIG. 11 is a sectional view of a transmissive and reflective type LCD inaccordance with another embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Now, exemplary embodiments of the present invention will be described indetail with reference to the annexed drawings.

FIG. 4 is a sectional view of a transmissive and reflective type LCD inaccordance with an embodiment of the present invention.

Referring to FIG. 4, the transmissive and reflective type LCD includes afirst substrate 110, a second substrate 130 of which an inner surface isarranged facing the first substrate 110, and a liquid crystal layer 150formed between the first substrate 110 and the second substrate 130.

The first and second substrates 110 and 130 are preferably manufacturedusing a glass substrate.

A first transparent electrode 115 is formed on the inner surface of thefirst substrate 110. Preferably, the first transparent electrode 115 isformed of conductive oxide film such as indium tin oxide (ITO).Preferably, the first transparent electrode 115 is elongated in a firstdirection, and serves as a signal electrode that is repeatedly arrangedin a second direction orthogonal to the first direction.

A first polarizing plate 155 is disposed on the outer surface of thefirst substrate 110. A second polarizing plate 165 is formed on an outersurface of the second substrate 130, opposite the inner surface of thesecond substrate 130. The first and second polarizing plates 155 and 165function to absorb polarized light and to transmit other polarizedlight, thereby allowing incident light to be transmitted in a specificdirection. The first and second polarizing plates 155 and 165 are linearpolarizers of which polarizing axes are arranged to be orthogonal toeach other.

A backlight 170 is installed at a rear side of the first polarizingplate 155.

A second transparent electrode 135 made of conductive oxide film such asITO is formed on the inner surface of the second substrate 130 facingthe first substrate 110. Preferably, the second transparent electrode135 serves as a scanning electrode that is repeatedly arranged in asecond direction and is elongated in the first direction. In otherwords, in a passive matrix type LCD, the first transparent electrode 115of the first substrate 110 and the second transparent electrode 135 ofthe second substrate 130 are arranged to be orthogonal to each othersuch that they are used as the signal electrode and scanning electrode,respectively.

The liquid crystal layer 150 is made of 270° super twisted nematic (STN)liquid crystal. Alternatively, the liquid crystal layer 150 can be madeof 90° twisted nematic (TN) liquid crystal. One skilled in the artreadily appreciates that the passive matrix type LCD uses STN liquidcrystal while the active matrix type LCD uses TN liquid crystal.

According to an embodiment of the present embodiment, the liquid crystallayer 150 has an Δnd of about 0.2 μm to about 0.6 μm that is a productof a refractive anisotropy Δn and a thickness d of the liquid crystallayer 150, preferably about 0.48 μm. The value of about 0.48 μm allowsthe LCD of the present invention to identically use an LC opticalcondition of the conventional transmission type LCD withoutmodification, thereby preventing the reliability of the liquid crystalfrom being lowered.

A transflective film 160 is disposed between the first polarizing plate155 and the backlight 170. The transflective film 160 includes at leasttwo transparent layers having a different refractivity index from eachother. A first layer 161 and a second layer 162 are preferablyalternatively stacked as shown in FIG. 5. The transparent transflectivefilm 160 functions to partially reflect and transmit incident light.Accordingly, the transmissive and reflective type LCD in accordance withan embodiment of the invention has a reflection light path 180 and atransmission light path 185. In the reflection light path, incidentlight is incident toward the second substrate 130, is transmittedthrough the first substrate 110, is reflected by the transflective film160, and is output through the second substrate 130. In the transmissionlight path 185, incident light is incident from the backlight onto thetransflective film 160 and the first substrate 110, and is outputthrough the second substrate 130.

Hereinafter, the structure and operations of the transflective film 160are described.

Referring to FIG. 5, when it is assumed that the transflective film 160has a film thickness direction of z-axis and a film plane of x-y plane,the transflective film 160 according to an aspect of the presentinvention is characterized in that the first layer 161 thereof has arefractive anisotropy within the film plane, e.g., x-y plane, and thesecond layer 162 does not have a refractive anisotropy within the filmplane.

The transflective film 160 has various transmissivity and reflectivitycharacteristics depending on polarizing state and direction of theincident light. For instance, when it is assumed that a directionparallel to an elongated direction of the transflective film 160 isx-direction and a direction perpendicular to the elongated direction isy-direction, each of the first layer 161 having a high refractivity andrefractive anisotropy within the film plane and the second layer 162 nothaving refractive anisotropy have three main refractive indexes ofn_(x), n_(y), and n_(z) that satisfy the following relationships (1):n1_(x)=n1_(z)≠n1_(y);n2_(x)=n2_(y)=n2_(z);n1_(x)≠n2_(x);n1_(y)≠n2_(y); and|n1_(x) −n2_(x) |<|n1_(y) −n2_(y)|  (1).

(n1x, n1y, and n1z denotes a main refractive index of the first layer inan x-axis, a y-axis, and a z-axis, respectively, and n2x, n2y, and n2zdenotes a main refractive index of the second layer in an x-axis, ay-axis, and a z-axis, respectively)

Thus, if a refractivity difference in the x-direction between the firstlayer 161 and the second layer 162 is less than a refractivitydifference in the y-direction between the first layer 161 and the secondlayer 162, when a non-polarized light is incident in the directionperpendicular to the film plane, i.e., z-direction, a polarizationcomponent polarized parallel to the y-direction is mostly reflected dueto a high difference in the refractivity based on Fresnel's equation,but a polarization component polarized parallel to the x-direction ispartially transmitted and reflected due to a low difference in therefractivity.

There are disclosed methods for enhancing the display brightness byusing a reflection type polarizing plate made of dielectric multilayeredfilm having birefringence in Japanese Patent Laid Open Publication No.9-506985 and International Patent Publication No. WO 97/01788. Thedielectric multilayered film having birefringence has a structure inwhich two kinds of polymer layers are alternatively stacked. One of thetwo kinds of polymer layers is selected from a polymer group having ahigh refractivity and the other is selected from a polymer group havinga low refractivity.

Hereinafter, the structure of the dielectric multilayered film isreviewed in an aspect of optical property.

For instance, when it is assumed that there is the followingrelationship between the first layer in which a material having a highrefractivity is elongated, and a second layer in which a material havinga low refractivity is elongated:n1_(x)=n1_(z)=1.57, n1_(y)=1.86; andn2_(x)=n2_(y)=n2_(z)=1.57.

Thus, in case that refractivities of the first and second layers in thex-direction and the z-direction are identical and refractivities of thefirst and second layers in the y-direction are different from eachother, when non-polarized light is incident in the directionperpendicular to the film plane, i.e., z-direction, polarizationcomponents in the x-direction are all transmitted, polarizationcomponents in the y-direction are all reflected based on Fresnel'sequation. A representative example of birefringence dielectricmultilayered films having the above characteristics is DBEF (Dualbrightness enhancement film). The DBEF has a multilayered structure inwhich two kinds of films made of different material are a few hundredlayers stacked. In other words, poly(ethylene naphtalate) layer having ahigh birefringence and poly(methyl methacrylate) (PMMA) layer arealternatively stacked to form the DBEF layer. Since naphthalene groupsof the poly(ethylene naphtalate) layer has a flat plane structure, whenthose groups are adjacently placed to each other, it is easy to stackthe poly(ethylene naphtalate) layer and the DBEF layer, so that therefractivity in the stacking direction becomes considerably differentfrom those in other directions. On the contrary, since the PMMA is anamorphous polymer and is isotropically aligned, the PMMA has anidentical refractivity in all directions.

The DBEF transmits all x-directional polarization components andreflects all y-directional polarization components, while thetransflective film 160 according to an aspect of the present inventionmostly reflects a specific-directional (for instance, y-directional)polarization component, but partially reflects and transmitspolarization component, which is polarized in a direction (for instance,x-direction) orthogonal to the specific direction. The transflectivefilm can be made by vertically attaching two anisotropic transflectivefilms having various transmissivity and reflectivity depending onpolarizing state and direction of an incident light. Alternatively, thetransflective film can be made by attaching an anisotropic transflectivefilm having various transmissivity and reflectivity depending onpolarizing state and direction of incident light and a transflectivefilm having isotropic reflection and transmission characteristicsregardless of polarizing state and direction of incident light. The twotransflective films can be made in an integrally formed structure, ormade in a separately formed film structure.

Also, according to another preferred aspect of the invention, thetransflective film 160 has isotropic reflection and transmissioncharacteristics regardless of polarizing state and direction of incidentlight. For instance, if it is assumed that a direction parallel to anelongated direction of the film is in the x-direction and a directionperpendicular to the elongated direction of the film is in they-direction, the first layer 161 having a high refractivity and thesecond layer 162 having a low refractivity both have a refractiveisotropy within x-y planes of the film, and each of the first and secondlayers 161 and 162 have three main refractive indexes of n_(x), n_(y),and n_(z) that satisfy the following relationships:n1_(x)=n1_(y)=n1_(z); andn2_(x)=n2_(y)=n2_(z)≠n1_(z)  (2).

Thus, in case that the first and second layers 161 and 162 havedifferent refractivity indexes in the z-direction, when non-polarizedlight is incident in the direction (i.e., z-direction) perpendicular tothe film, polarization components in the x-direction are partiallytransmitted and reflected according to Fresnels's equation, andpolarization components in the y-direction are partially transmitted andreflected. At this time, the reflectivity of reflected light can beadjusted to match with characteristics of the transmissive andreflective type LCD by controlling the thickness or the refractivity ofthe first layer 161 or the second layer 162. In other words, areflection characteristic-enhanced transmissive and reflective type LCDenhances the reflectivity, whereas a transmissive and reflective typeLCD in which transmission characteristic is considered to be animportant issue, lowers the reflectivity to thereby enhance thetransmissivity.

As described above, the transflective film 160 of the present inventioncan be formed to have an anisotropy characteristic in whichtransmissivity and reflectivity of the film 160 varies with polarizingstate and direction of incident light, or can be formed to have anisotropy characteristic in which transmissivity and reflectivity of thefilm 160 do not depend on polarizing state and direction of the incidentlight. In any case, it is desirable that the transflective film 160 hasa reflectivity of no less than about 4% with respect to polarizationcomponent in all directions when light is incident in a directionperpendicular to the film plane.

According to an embodiment of the present invention, the transflectivefilm 160 can be made in an integrally formed structure together with thefirst polarizing plate 155, or made in a separately formed filmstructure separated from the first polarizing plate 155. In case thatthe transflective film 160 is made in an integrally formed structuretogether with the first polarizing plate 155, it is possible to decreasethe thickness of the LC cell, and the LCD has an advantage in an aspectof manufacturing cost.

In the above, there is explained a method of forming the transflectivefilm 160 by depositing or coating a multilayered polymer film on asurface of the first polarizing plate 155. This method differs from ananti-reflection treatment in the polarizing plate. In other words, inthe anti-reflection treatment, two kinds of transparent films havingdifferent refractivity are repeatedly deposited or coated in a constantthickness such that destructive interference occurs by multi-reflectionwithin the multilayered polymer film. However, to form a transflectivefilm capable of partially transmitting and partially reflecting incidentlight, the film thickness should be adjusted such that constructiveinterference occurs.

FIGS. 6A and 6B are sectional views for illustrating a light scatteringlayer that is applicable to the transmissive and reflective type LCD ofFIG. 4;

Referring to FIGS. 6A and 6B, the transmissive and reflective type LCDfurther includes a light scattering layer 168 formed on the firstsubstrate 110 or the second substrate 130 to prevent specular reflectionand to properly diffuse a reflected light in various angles. Forinstance, it is possible to form the light scattering layer 168 betweenthe first substrate 110 and the first polarizing plate 155, between thesecond substrate 130 and the second polarizing plate 165, or between thefirst polarizing plate 155 and the transflective film 160. The lightscattering layer 168 can be made in an integrally formed structuretogether with the first polarizing plate 155 or the second polarizingplate 165, or made in a separate film structure separated from thepolarizing plates 155 and 165. Further, the light scattering layer 168can be made in a form of a plastic film in which transparent beads aredispersed. Moreover, the light scattering layer 168 can be made in astate in which beads are added to an adhesive, which makes it possibleto directly attach the first substrate 110 to the first polarizing plate155.

Furthermore, to optimize light efficiency in the transmissive andreflective type LCD, it is possible to form a phase difference plate(not shown) on the first substrate 110 or the second substrate 130. Forinstance, the phase difference plate is formed in an integrally formedstructure together with polarizing plate or a separate film structureseparated from the polarizing plate between the first substrate 110 andthe first polarizing plate 155, or between the second substrate 130 andthe second polarizing plate 165.

Hereinafter, there is described in detail an operation mechanism of thetransmissive and reflective type LCD having the above structure.

FIG. 7A through FIG. 8B are schematic views for illustrating operationsin reflection mode and transmission mode in the transmissive andreflective type LCD in which the transflective film 160 is made anintegrally formed structure together with the first polarizing plate155. Here, polarization directions of the light are represented on thebasis of a polarizing axis of the second polarizing plate 165, and apartially reflected light and a partially transmitted light by a dottedline.

First, when a pixel voltage is not applied (OFF) in the reflection mode,as shown in FIG. 7A, light that is incident from an outside istransmitted through the second polarizing plate 165, so that the lightis linearly polarized in a direction parallel to the polarizing axis ofthe second polarizing plate 165. The linearly polarized light istransmitted through the liquid crystal layer 150 and the firsttransparent electrode 115, so that the linearly polarized light islinearly polarized in a direction perpendicular to the polarizing axisof the second polarizing plate 165 and is then incident onto thetransflective film 160 made an integrally formed structure together withthe first polarizing plate 155. At this time, since the polarizing axisof the first polarizing plate 155 is orthogonal to that of the secondpolarizing plate 165, the light that is incident onto the firstpolarizing plate 155 is parallel to the polarizing axis of the firstpolarizing plate 155. Accordingly, the light linearly polarized in thedirection parallel to the polarizing axis of the first polarizing plate155 is partially transmitted through the transflective film 160 and ispartially reflected by the transflective film 160. In other words, incase that the transflective film 160 has the refractivity characteristicof the relationship (1), a polarization component, which is polarized inthe x-direction parallel to the elongated direction of the transflectivefilm 160, in the lights that are incident onto the transflective film160 is partially transmitted and reflected, whereas a polarizationcomponent which is polarized in the direction perpendicular to theelongated direction is mostly reflected. Further, in case that thetransflective film 160 has the refractive characteristic of therelationship (2), in the lights that are incident onto the transflectivefilm 160, the polarization components which is polarized in the x- andy-directions are partially transmitted and partially reflected.

Thus, the linearly polarized light reflected by the transflective film160 is transmitted through the first transparent electrode 115 and theliquid crystal layer 150, so that it is linearly polarized in thedirection parallel to the polarizing axis of the second polarizing plate165. Afterwards, the light is transmitted through the second polarizingplate 165, so that a white image is displayed. Also, the lights thathave been transmitted through the transflective film 160 are restoredbetween the transflective film 160 and the backlight 170, and therestored lights repeatedly carry out a procedure of a partial reflectionand a partial transmission. As a consequence, light loss is eliminatedand reflectivity and light efficiency are enhanced.

When a maximum pixel voltage is applied (ON) in the reflection mode, asshown in FIG. 7B, light that is incident from an outside is transmittedthrough the second polarizing plate 165, so that the light is linearlypolarized in a direction parallel to the polarizing axis of the secondpolarizing plate 165. Afterwards, the linearly polarized light istransmitted through the liquid crystal layer 150 without a variation inthe polarizing state, and is then incident onto the transflective film160 integrally formed with the first polarizing plate 155. At this time,since the linearly polarized light is perpendicular to the polarizingaxis of the first polarizing plate 155, the light is all absorbed in thefirst polarizing plate 155. Thus, the linearly polarized light is notreflected by the transflective film 160, so that a black image isdisplayed.

When a pixel voltage is not applied (OFF) in the transmission mode, asshown in FIG. 8A, light that is irradiated from the backlight 170 isincident onto the transflective film 160 integrally formed with thefirst polarizing plate 155. In case that the transflective film 160 hasthe refractive characteristic of the relationship (1), a polarizationcomponent, which is polarized parallel to the x-direction in the lightsthat are parallel to the polarizing axis of the first polarizing plate155, is partially transmitted and reflected, whereas a polarizationcomponent which is polarized parallel to the y-direction is mostlyreflected. Also, in case that the transflective film 160 has therefractive characteristic of the relationship (2), lights which areparallel to the polarizing axis of the first polarizing plate 155 arepartially transmitted and partially reflected because all polarizationcomponents which are polarized in the x-direction and y-direction ispartially transmitted and reflected.

Thus, the light that has been transmitted through the transflective film160 and the first polarizing plate 155 becomes a linearly polarizedlight having a propagating direction parallel to the polarizing axis ofthe first polarizing plate 155. The linearly polarized light istransmitted through the first transparent electrode 115 and the liquidcrystal 150, so that it is linearly polarized in a direction parallel tothe polarizing axis of the second polarizing plate 165. Accordingly, thelight linearly polarized in the direction parallel to the polarizingaxis of the second polarizing plate 165 is transmitted through thesecond polarizing plate 165, so that a white image is displayed. Also,light reflected by the transflective film 160 is restored between thebacklight 170 and the transflective film 160, and then repeats to carryout the above steps. Thus, polarization components parallel to thex-direction or polarization components parallel to the x- andy-directions are continuously transmitted through the transflective film160 and are used, so that light loss is eliminated and transmissivityand light efficiency are enhanced.

When a maximum pixel voltage is applied (ON) in the transmission mode,as shown in FIG. 8B, light that is irradiated from the backlight 170 isincident onto the transflective film 160 integrally formed with thefirst polarizing plate 155, so that the light parallel to the polarizingaxis of the first polarizing plate 155 is partially transmitted andreflected. The light that has been transmitted through the transflectivefilm 160 and the first polarizing plate 155, is converted onto lightlineally polarized in the direction parallel to the polarizing axis ofthe first polarizing plate 155, i.e., in the direction perpendicular tothe polarizing axis of the second polarizing plate 165. The linearlypolarized light is transmitted through the first transparent electrode115 and the liquid crystal layer 150 without a variation in thepolarizing state. Accordingly, the light linearly polarized in thedirection perpendicular to the polarizing axis of the second polarizingplate 165 is not transmitted through the second polarizing plate 165, sothat a black image is displayed.

FIG. 9A through FIG. 10B are schematic views for illustrating thetransmission mode and the reflection mode of a transmissive andreflective type LCD in which the transflective film 160 is separatedfrom the first polarizing plate 155 and is made in a film structure.Here, polarization directions of the light are represented on the basisof a polarizing axis of the second polarizing plate 165, and partiallyreflected light and partially transmitted light by a dotted line.

First when a pixel voltage is not applied (OFF) in the reflection mode,as shown in FIG. 9A, light that is incident from an outside istransmitted through the second polarizing plate 165, so that the lightis linearly polarized in a direction parallel to the polarizing axis ofthe second polarizing plate 165. The linearly polarized light istransmitted through the liquid crystal layer 150 and the firsttransparent electrode 115, so that the linearly polarized light islinearly polarized in a direction perpendicular to the polarizing axisof the second polarizing plate 165 and is then incident onto the firstpolarizing plate 155. At this time, since the polarizing axis of thefirst polarizing plate 155 is orthogonal to that of the secondpolarizing plate 165, the light that has been linearly polarized in adirection perpendicular to the polarizing axis of the second polarizingplate 155 is transmitted through the first polarizing plate 155 and isthen incident onto the transflective film 160. In case that thetransflective film 160 has the refractivity characteristic defined inequation (1), a polarization component, which is polarized in thex-direction parallel to the elongated direction of the transflectivefilm 160, light rays directed incident to the transflective film 160 ispartially transmitted and reflected, whereas a polarization component,which is polarized in the y-direction perpendicular to the elongateddirection, is mostly reflected. Further, in case that the transflectivefilm 160 has the refractive characteristic of the relationship (2),light rays that are incident to the transflective film 160, thepolarization components polarized in the x- and y-directions arepartially transmitted and partially reflected.

Thus, since the linearly polarized light reflected by the transflectivefilm 160 is parallel to the polarizing axis of the first polarizingplate 155, it is transmitted through the first polarizing plate 155, andis incident onto the liquid crystal layer 150 via the transparentelectrode 115. The linearly polarized light is transmitted through theliquid crystal layer 150, whereby it is linearly polarized in thedirection parallel to the polarizing axis of the second polarizing plate165. Afterwards, the light is transmitted through the second polarizingplate 165, so that a white image is displayed. Also, the light rays thathave been transmitted through the transflective film 160 are restoredbetween the transflective film 160 and the backlight 170, and therestored light repeatedly carry out a procedure of a partial reflectionand a partial transmission. As a consequence, light loss is eliminatedand reflectivity and light efficiency are enhanced.

When a maximum pixel voltage is applied (ON) in the reflection mode asshown in FIG. 9B, light that is incident from an outside is transmittedthrough the second polarizing plate 165, so that the light is linearlypolarized in a direction parallel to the polarizing axis of the secondpolarizing plate 165. Afterwards, the linearly polarized light istransmitted through the liquid crystal layer 150 without a variation inthe polarizing state, and is then incident onto the first polarizingplate 155. At this time, since the linearly polarized light isperpendicular to the polarizing axis of the first polarizing plate 155,the light is all absorbed in the first polarizing plate 155. Thus, sincethe linearly polarized light is not reflected by the transflective film160, a black image is displayed.

When a pixel voltage is not applied (OFF) in the transmission mode, asshown in FIG. 10A, light that is irradiated from the backlight 170 isincident onto the transflective film 160, so that the light is partiallytransmitted and reflected. In case that the transflective film 160 hasthe refractive characteristic of the relationship (1), polarizationcomponents, which is polarized in the x-direction parallel to theelongated direction of the transflective film 160. in the lights thathave been incident onto the transflective film 160 is partiallytransmitted and reflected, whereas polarization components, which ispolarized in the y-direction perpendicular to the elongated direction,are mostly reflected. Also, in case that the transflective film 160 hasthe refractive characteristic of the relationship (2), polarizationcomponents, which is polarized in the x- and y-directions, in the lightsthat have been incident onto the transflective film 160 are partiallytransmitted and reflected.

Thus, the light that has been transmitted through the transflective film160 and the first polarizing plate 155 is linearly polarized in adirection parallel to the polarizing axis of the first polarizing plate155. Afterwards, the linearly polarized light is transmitted through thefirst transparent electrode 115 and the liquid crystal 150, so that itis linearly polarized in a direction parallel to the polarizing axis ofthe second polarizing plate 165. Accordingly, the light linearlypolarized in the direction parallel to the polarizing axis of the secondpolarizing plate 165 is transmitted through the second polarizing plate165, so that a white image is displayed. Also, light reflected by thetransflective film 160 is restored between the backlight 170 and thetransflective film 160, and then repeats to carry out the above steps.Thus, polarization components polarized parallel to the x-direction orpolarization components polarized parallel to the x- and y-directionscontinuously is transmitted through the transflective film 160 and areused, so that light loss is eliminated and transmissivity and lightefficiency are enhanced.

When a maximum pixel voltage is applied (ON) in the transmission mode,as shown in FIG. 10B, light that is irradiated from the backlight 170 isincident onto the transflective film 160, so that the incident light ispartially transmitted through the transflective film 160 and ispartially reflected by the transflective film 160. The light that hasbeen transmitted through the transflective film 160 is transmittedthrough the first polarizing plate 155, so that it is converted ontolight lineally polarized parallel to the polarizing axis of the firstpolarizing plate 155, i.e., a direction perpendicular to the polarizingaxis of the second polarizing plate 165. Afterwards, the linearlypolarized light is transmitted through the first transparent electrode115 and the liquid crystal layer 150 without a variation in thepolarizing state. Accordingly, the light linearly polarized in thedirection perpendicular to the polarizing axis of the second polarizingplate 165 cannot be transmitted through the second polarizing plate 165,so that a black image is displayed.

FIG. 11 is a sectional view of a transmissive and reflective type LCD inaccordance with another embodiment of the present invention.

Referring to FIG. 11, a transmissive and reflective type LCD includes afirst substrate 200, a second substrate 250 arranged facing the firstsubstrate 200, a liquid crystal layer 260 formed between the firstsubstrate 200 and the second substrate 250, and a backlight 270 arrangedat a rear side of the first substrate 200.

The first substrate 200 includes a first insulating substrate 210. Aplurality of gate lines (not shown) and a plurality of data lines (notshown) are formed on the first insulating substrate 210 in a matrixconfiguration. A pixel electrode 234 and a thin film transistor 225 areformed at a region defined by a pair of gate line and a pair of datalines. The second substrate 250 includes a second insulating substrate252, a color filter 254 of RGB pixels, for displaying colors while lightis transmitted therethrough, a black matrix 256 for preventing lightfrom being leaked between pixels, and a transparent common electrode258.

A thin film transistor 225 includes a gate electrode 212 formed on thefirst insulating substrate 210, a gate insulating film 214 formed on thegate electrode 212 and the first insulating substrate 210, an activepattern 216 and an ohmic contact pattern 218 both formed on the gateinsulating film 214 on the gate electrode 212, and source and drainelectrodes 220 and 222 formed apart from each other on the ohmic contactpattern 218. A passivation film 230 made of organic or inorganicsubstance is formed on the first insulating substrate 210 including thethin film transistor 225. A contact hole 232 penetrating the passivationfilm 230 is formed in the passivation film 230 to expose the drainelectrode 222. The pixel electrode 234 is made of transparent conductiveoxide such as ITO (Indium tin oxide).

The liquid crystal layer 260 is made of 90° twisted nematic (TN) liquidcrystal, and has a Δnd of about 0.2 μm to about 0.6 μm that is a productof a refractive anisotropy Δn and a thickness d of the liquid crystallayer 260, preferably about 0.48 μm. Thus, the value on the refractivityanisotropy allows the LCD of the present invention to use the LC opticalcondition of the conventional transmission type LCD without anymodification, thereby preventing the reliability of the liquid crystalfrom being lowered.

Depending on alignment direction of the liquid crystal layer 260, firstand second polarizing plates 262 and 266 for transmitting only lightpropagating in a specific direction are respectively attached on outersurfaces of the first and second substrates 210 and 252. Preferably, thefirst and second polarizing plates 262 and 266 are linear polarizers ofwhich polarizing axes are arranged perpendicular to each other.

The gate electrode 212 of the thin film transistor 225 is connected tothe gate line, the source electrode 220 is connected to the data line,and the drain electrode 222 is connected to the pixel electrode 234through the contact hole 232. Accordingly, as a scanning voltage isapplied to the gate electrode 212, a signal voltage flowing through thedata line is applied to the drain electrode 222 through the activepattern 216 from the source electrode 220. If the signal voltage isapplied to the drain electrode 222, there is generated a voltagedifference between the pixel electrode 234 connected to the drainelectrode 222 and the common electrode 258 of the second substrate 252.As a consequence, molecular arrangement of the liquid crystal layer 260injected between the pixel electrode 234 and the common electrode 258varies, and thereby light transmissivity through the liquid crystallayer 260 varies. Thus, the thin film transistor 225 performs the roleas switching element for turning on or turning off pixels of the LCcell.

According to an embodiment of the present invention, a transflectivefilm 264 is formed between the first polarizing plate 262 and thebacklight 270. The transflective film 264 is formed of a plurality oftransparent layers in which first and second layers (not shown) havingdifferent refractivity are alternatively stacked. As described in theabove embodiment, the transflective film 264 functions to partiallytransmit and reflect the incident light. In other words, thetransflective film 264 can be formed in a structure having anisotropycharacteristic in which degrees of the transmissivity and thereflectivity vary with polarizing state and direction of the incidentlight, or in a structure having isotropy characteristic in which degreesof the transmissivity and the reflectivity do not vary with polarizingstate and direction of the incident light. In any cases, it is desirablethat the transflective film 264 is formed to have about 4% or more inthe reflectivity with respect to polarization components in alldirections. The transflective film 264 is formed in an integrally formedstructure with the first polarizing plate 262 or in a structureseparated from the first polarizing plate 262.

Further, to prevent specular reflection and properly diffuse reflectedlights in several directions, the transmissive and reflective type LCDin accordance with the present embodiment can further include a lightscattering layer (not shown) on either the first substrate 200 or thesecond substrate 250. For instance, the light scattering layer can beformed between the first substrate 200 and the first polarizing plate262, between the second substrate 250 and the second polarizing plate266, or between the first polarizing plate 262 and the transflectivefilm 264. The light scattering layer is formed in an integrally formedstructure with the first polarizing plate 262 or the second polarizingplate 266, or in a structure separated from the first polarizing plate262 or the second polarizing plate 266. Also, the light scattering layercan be made by mixing adhesive and beads.

Moreover, to optimize light efficiency in the transmissive andreflective type LCD of the present embodiment, a phase differentialplate (not shown) can be further formed on either the first substrate200 or the second substrate 250. For instance, the phase differentialplate is formed between the first substrate 200 and the first polarizingplate 262 or between the second substrate 250 and the second polarizingplate 266. Also, the phase difference plate is formed in an integrallyformed structure with the first polarizing plate 262 or the secondpolarizing plate 266, or in a structure separated from the firstpolarizing plate 262 or the second polarizing plate 266.

According to the transmissive and reflective type LCD of the presentembodiment, a reflection electrode is not formed within the LC cell, butthe transflective film 264 substitutes for the reflection electrode, andperforms the role of the reflection electrode. Accordingly, light thatis incident toward the second substrate 252 from an outside has areflection light path 280 in which the light is transmitted through thefirst substrate 210, is reflected by the transflective film 264, and isoutput through the second substrate 252. Also, light that is incidenttoward the first substrate 200 from the backlight 270 has a transmissionlight path 285 in which the light is transmitted through thetransflective film 264 and then is output through the second substrate250.

The transmissive and reflective type LCD shown in FIG. 11 has the sameoperation mechanism in the reflection mode and the transmission mode asthose described with reference to FIG. 7A through FIG. 10B. In otherwords, by using the transflective film 264 which partially transmits andreflects the incident light, light loss is not generated in thereflection mode and the transmission mode, so that it is possible toenhance both of the reflectivity and transmissivity. Also, compared withthe conventional transmissive and reflective type LCD of FIG. 1, thetransmissive and reflective type LCD of the present invention does notrequire a ¼-wavelength phase difference plate on the lower substrate,i.e., the first substrate 210. Further, light that is incident from thebacklight 270 and is reflected from regions where a metal layer, such asthe gate line or data line, exists within the LC cell, are restoredbetween the transflective film 264 and the backlight 270 and therestored lights are used, so that it increases overall light efficiency.

As described above, according to a preferred embodiment of the presentinvention, between the first polarizing plate attached on the outersurface of the lower substrate (i.e., first substrate) and the backlightis formed an anisotropy transflective film having an opticalcharacteristic in which light components in a specific direction arestrongly reflected and polarization components in a directionperpendicular to the specific direction are partially transmitted andreflected depending on polarizing state and direction of an incidentlight, or an isotropy transflective film having an opticalcharacteristic in which light components are partially transmitted andreflected regardless of polarizing state and direction of the incidentlight. As a result, by a restoring process of light occurring betweenthe transflective film and the backlight, the restored light istransmitted through the transflective film repeatedly, so thattransmissivity and light efficiency are enhanced.

Further, the transmissive and reflective type LCD according to apreferred embodiment of the present invention does not require areflection electrode within LC cell or a ¼-wavelength phase differenceplate on each of the upper substrate (second substrate) and the lowersubstrate (first substrate). Accordingly, compared with the conventionaltransmissive and reflective type LCD, the transmissive and reflectivetype LCD of the present invention is simpler and can be more easilymade.

Furthermore, since the optical conditions applied to the liquid crystalof the conventional transmissive and reflective type LCD can beidentically applied to that of the transmissive and reflective type LCDof the present invention, there is no degradation in reliability.

While the present invention has been described in detail, it should beunderstood that various changes, substitutions and alterations can bemade hereto without departing from the spirit and scope of the inventionas defined by the appended claims.

1. A transmissive and reflective type LCD comprising: a first substrate;a second substrate having an inner surface facing the first substrate; aliquid crystal layer formed between the first substrate and the secondsubstrate; a first polarizing plate formed on an outer surface of thefirst substrate; a second polarizing plate formed on an outer surface ofthe second substrate; a backlight for irradiating incident light ontothe first polarizing plate; and a transflective film arranged betweenthe first polarizing plate and the backlight, the transflective filmpartially reflecting and transmitting a first polarization component ofthe incident light polarized in a first direction and a secondpolarization component of the incident light polarized in a seconddirection orthogonal to the first direction.
 2. The transmissive andreflective type LCD of claim 1, wherein the transflective film hasisotropic transmission and reflection characteristics independent ofpolarizing state and direction of the incident light.
 3. Thetransmissive and reflective type LCD of claim 2, wherein thetransflective film includes at least a first layer and a second layer,and each of the first layer and the second layer has three mainrefractive indexes of n_(x), n_(y), and n_(z) that satisfy the followingrelationships:n1_(x)=n1_(y)=n1_(z); andn2_(x)=n2_(y)=n2_(z)≠n1_(z), wherein the transflective film has athickness direction of z-axis and a film plane of x-y plane, whereinn1x, n1y and n1z denotes a main refractive index of the first layer inan x-axis, y-axis, and z-axis, respectively, and n2x, n2y and n2zdenotes a main refractive index of the second layer in an x-axis, y-axisand z-axis, respectively.
 4. A transmissive and reflective type LCD forpartially reflecting and transmitting incident light, comprising: an LCcell including a first substrate, a second substrate having an innersurface that is arranged to face the first substrate, and a liquidcrystal layer formed between the first substrate and the secondsubstrate; a first polarizing plate formed on an outer surface of thefirst substrate; a second polarizing plate formed on an outer surface ofthe second substrate; a backlight arranged at a rear side of the firstpolarizing plate; and a transparent transflective film arranged betweenthe first polarizing plate and the backlight and having a plurality oflayers in which a first layer and a second layer have differentrefractivity indexes from each other, the transflective film partiallyreflecting the transmitting a first polarization component of theincident light polarized in a first direction and a second polarizationcomponent of the incident light polarized in a second directionorthogonal to the first direction, wherein the transmissive andreflective type LCD has a reflection light path along which the incidentlight is incident onto the LC cell from a front side of the LC cell, isreflected by the transflective film, and is output through the frontside of the LC cell, and a transmission light path along which theincident light is incident onto the LC cell from a rear side of the LCcell, is transmitted through the transflective film, and is outputthrough the front side of the LC cell.
 5. The transmissive andreflective type LCD of claim 4, wherein the transflective film hasisotropic transmission and reflection characteristics independent ofpolarizing state and direction of the incident light.
 6. Thetransmissive and reflective type LCD of claim 5, wherein each of thefirst layer and the second layer has three main refractive indexes ofn_(x), n_(y), and n_(z) with the following relationships:n1_(x)=n1_(y)=n1_(z); andn2_(x)=n2_(y)=n2_(z)≠n1_(z),wherein the transflective film has athickness direction of z-axis and a film plane of x-y plane, whereinn1x, n1y, and n1z denotes a main refractive index of the first layer inan x-axis, y-axis, and z-axis, respectively, and n2x, n2y, and n2zdenotes a main refractive index of the second layer in an x-axis,y-axis, and z-axis, respectively.